Various digital audio input/output audio interfaces for A/V systems are in common use, like IEC958 and ADAT for digital IO, or AC-Link and I2S primarily for connection to AD/DA converters. Nowadays, a typical interface application often requires more than a single type of interface. Known building blocks for such interfaces usually implement a single interface. A receiver for example consists of a protocol decoder outputting clean data bits and a bit clock for the subsequent serial-to-parallel converter forming from the serial data bit stream a sequence of sample words. The sample words are then written to a memory of the processing system, using e.g. DMA (direct memory access) and/or interrupt or polling data transfer and, if required, a FIFO for buffering the audio data. A transmitter will consist of similar components implementing the corresponding opposite data processing direction. Typical systems will use DMA for the data transfer, due to the ratio of processor clock and audio sampling frequency. The basic DMA transfer operation can be done by software if processing speed does not matter. The following refers sometimes to the use of DMA, but DMA input and output can be replaced in the invention in each case by interrupt or polling mechanisms.
An interface specialised for a single protocol (like a IEC958 receiver) will typically also use a specialised serial-to-parallel converter (or parallel-to-serial converter in case of transmitter), i.e. one that implements MSB first or LSB first, number of bits etc according to the interface requirements.